1. Field of the Invention
The present invention relates to semiconductor devices including photosensors. The present invention relates to a semiconductor device including a photosensor and a display element, and more particularly to a semiconductor device including a light-emitting element as a display element. In addition, the present invention relates to a method for driving a semiconductor device and an electronic device including a semiconductor device.
2. Description of the Related Art
An example of a semiconductor device including a matrix of a plurality of sensors that detect light (also referred to as photosensors) is a solid-state imaging device (also referred to as an image sensor) used in electronic devices such as digital still cameras and mobile phones.
In particular, a semiconductor device including a matrix of a plurality of combinations of photosensors and display elements has an image display function in addition to an image capture function, and is called a touch panel, a touchscreen, or the like (hereinafter referred to as a touch panel). In a touch panel, a region where combinations of photosensors and display elements are arranged in matrix serves as a region for displaying images and inputting data (hereinafter referred to as a display and data input region).
There is suggested a touch panel that uses a display element including an organic light-emitting element as a display element and has a display and data input region where combinations of photosensors and display elements including organic light-emitting elements are arranged in matrix (see FIG. 8 and FIG. 9 in Patent Document 1).
In the touch panel including display elements including light-emitting elements as the display elements, the light-emitting elements arranged in matrix are made to emit light first. When an object exists, the light is blocked by the object and partly reflected. The photosensors arranged in matrix detect the amount of light reflected from the object. In such a manner, the touch panel captures an image of the object and detects a region where the object exists.
With the method for driving the touch panel disclosed in Patent Document 1, a plurality of photosensors sequentially obtain data on an object (hereinafter also referred to as object data) corresponding to red row by row in a period during which the light-emitting elements emit red light; the plurality of photosensors sequentially obtain object data corresponding to green row by row in a period during which the light-emitting elements emit green light; and the plurality of photosensors sequentially obtain object data corresponding to blue row by row in a period during which the light-emitting elements emit blue light. In such a manner, a color image corresponding to the object is obtained (see FIG. 10 in Patent Document 1).